Referring to FIG. 1, a positioning architecture related to an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) generally includes an Evolved Serving Mobile Location Center (E-SMLC), a Mobility Management Entity (MME), a base station (eNB) and a User Equipment (UE).
A mobile location service is a service, for example, of emergent rescuing, deployed based upon the location of a UE. At present, two positioning methods are available as follows: control-plane location and secure user-plane location. Control-plane location refers to a positioning process in which an E-UTRAN signaling link is required so that the MME transmits a positioning request to the E-SMLC to trigger the positioning process and the E-SMLC returns a positioning result to the MME after performing positioning operations and in which the E-SMLC, the MME, the eNB, the UE, etc., may participate.
The E-SMLC translates a required location requested by a client into corresponding E-UTRAN measurement parameters, selects a positioning method and calculates a final result and precision from a returned estimation result of the location. The MME provides a Location service (LCS) with a mobility management function, which includes notifying the E-SMLC/a Gateway Mobile Location Center (GMLC) about movement of the UE. The eNB provides the E-SMLC with measurement result related to the location service, and passes auxiliary information required for the location service, etc. The UE provides the E-SMLC with measurement result related to the location service.
In an existing Long Term Evolution (LTE) system, a control-plane based positioning method includes :the Cell Identifier (Cell ID)+Timing Advance (TA)+Angle Of Arrival (AOA) scheme, the Observed Time Difference of Arrival (OTDOA) scheme, i.e., the Enhanced Cell Identity (E-CID) scheme, and the enhanced Requirements for Support of Assisted Global Navigation Satellite System (A-GNSS) scheme.
A general principle of the Cell ID+TA+AOA scheme is to obtain the angle of the user equipment to the base station relative to the north direction (i.e., AOA) and a TA of the user equipment to calculate the location. In the LTE, the TA can be obtained by being maintained at the user equipment or being measured at the base station.
The eNB obtains via an intelligent antenna the AOA at which the UE transmits a signal, and the UE is located on a ray which originates from the eNB and is rotated counterclockwise from the north direction by an angle of AOA.
Referring to FIG. 2, the Timing Advance (NTA) refers to the offset between uplink and downlink frame timings at the UE.
Referring to FIG. 3, it can be considered in view of a timing at the base station that NTA is typically embodied as twice a delay due to a distance d.
The distance between the UE and the eNB can be derived from NTA, and the UE is located on a circle with a center being at the eNB and a radius being the distance. The E-SMLC can calculate the location of the UE from the foregoing information and geographical location information of a serving cell.
The inventors have defined two types of TA report formats during their study: Type1 and Type2, where TADV represents information on a timing advance of a report.
Type1: TADV=(eNB Rx-Tx time difference)+(UE Rx-Tx time difference); and
Type2: TADV=eNB Rx-Tx time difference.
Wherein “UE Rx-Tx time difference” represents the difference between reception and transmission time at the user equipment and “eNB Rx-Tx time difference” represents the difference between reception time and transmission time at the base station.
However it is unknown for the eNB how to select an appropriate TA format in the existing Cell ID+TA+AOA positioning scheme, so there is a need of introducing a mechanism to ensure a timing advance of a report from the eNB.